Anomalous evolution of microstructure and crystallographic texture during indentation

Abstract The present work combines orientation imaging microscopy (OIM) and visco-plastic self-consistent framework based numerical simulation to study evolution of microstructure and crystallographic texture during indentation of copper. It was seen that anomalous microstructure evolution characteristics involving accelerated grain fragmentation and refinement resulted in ultra-fine grains at low equivalent strains within a zone close to the interface of the indenter. Sources of acceleration in refinement were found in enhanced local crystallographic rotation rates manifesting through micro-scale strain-path changes in pathlines leading into the zone near the interface. These strain path changes were shown to result from heterogeneous accommodation of deformation across mechanically harder/softer micro-zones prevalent in copper despite absence of a harder second phase. The micro-zones were recognized using Taylor factor analysis by coupling in-situ characterization of deformation fields with OIM. In addition to accelerated refinement, zones near the interface of the indenter also exhibited cube textures as opposed to shear-type textures elsewhere in the specimen, confirming a hitherto unknown heterogeneity in the geometry of deformation mechanics imposed during indentation.